1. Field of the Invention
The present invention relates to flow regulators for intravenous (IV) equipment and, more particularly, to a manually-operated regulator that allows interruption of normal controlled-flow for a safe and convenient bolus flush (full flow of saline for a specific period of time or volume of flush) before returning to a “pre-flush” flow setting, eliminating the need to manually reset the roller regulator or to administer a separate saline flush.
2. Description of the Background
Intravascular or IV sets deliver fluid, medications, blood products and parenteral nutrition to patients. Most IV machines operate by gravity or by an infusion pump (a pump, usually peristaltic, used to control the flow through the IV tube). FIG. 14 is a perspective view of a conventional IV administration set, which includes an injectable solution bag, opening to a drip chamber, connected by flexible tubing to a roller-clamp and on to a catheter adapter which can be coupled to a catheter for administration to a patient. Intravenous therapy is a complex process usually requiring the preparation of machine, IV lines and medicine before administration to the patient. This involves a number of considerations, such as air or gas bubble detection, gas removal, and flow rate control. Roller-clamps as in FIG. 14 are the most widely used flow control device. The roller-clamp comprises a wheel trapped within a housing that compresses the IV tubing as it is slid along a gradual ramp. The flow rate is calculated by counting drops in a drip chamber. The infusion can be driven by gravity alone, or by an electronic infusion pump. The US market for roller-clamp-type IV administration sets is estimated at 1.4 billion dollars.
To administer a drug into a patient using an existing IV set with a roller-clamp regulator, the drug is typically injected into the IV upstream (proximal) of where it enters the patient's body. Methods of administering IV medication may include giving the medication intermittently over a specific amount of time using a secondary IV line, or giving the medication continuously mixed in the main IV solution. IV push medication techniques deliver a bolus (a dose of medication injected all at once intravenously) of medication directly into a vein or access port to produce an immediate peak drug level in the patient's bloodstream. A bolus injection is most often given through a peripheral IV line, a saline lock, or through a vascular access port. After injection, a saline “flush” is necessary to ensure delivery of the medicine to the patient's circulation. To accomplish a flush, one of two methods is typically employed. First, the user may open the roller-clamp to full flow for a brief period of time, then return it to the desired setting once the drug has been flushed into the circulation. This method leaves open the possibility that the user will forget to return the clamp to the pre-flush setting, thus causing the accidental administration of a large volume of IV fluid (an event which at best is embarrassing but innocuous, and at worst fatal). A second method of administering a flush is to draw up a separate syringe of flush solution (typically saline). The separate saline flush is administered as a “chaser” through the same port as the injected medicine. This method is fraught with its own problems ranging from wasteful use of supplies to infection control issues.
Manufacturers are approaching this problem by trying to develop computerized IV machines that can administer preprogrammed amounts of saline chasers. These devices include a twin-head injector equipped with two syringes, one for saline and one for medication. The devices can be preprogrammed to control the quantity and injection rate of both medication and saline. For example, U.S. Pat. No. 6,641,562 to Peterson (HPS Medical, Inc.) issued Nov. 4, 2003 shows an apparatus and method of intravenous fluid infusion that uses a microcomputer to cyclically drive a fluid control module which outputs a fixed amount of medicine for each cycle of operation. Unfortunately, this and like systems are far more complicated than the classic roller regulator, more expensive and difficult to use. Moreover, they do not supplant the need for the traditional manual roller-clamp regulator which is still used to regulate the flow rate at baseline.
Given the problems associated with the traditional manner of administering a saline flush, it would be much more advantageous to provide a purely mechanical (or electromechanical) device (either incorporated into or separate from the roller-clamp) capable of delivering a saline flush following a bolus of medication.
The foregoing has been attempted in one known case. U.S. Pat. No. 6,500,156 to Stansbury (McKinley Medical L.L.L.P) issued Dec. 31, 2002 shows a thumb-powered flushing device for catheters in which a chamber is covered with a flexible diaphragm that can be compressed by exertion of pressure on the diaphragm to propel fluid through the catheter, and a valve that regulates flow into and out of the chamber beneath the movable member that pumps fluid to deliver a bolus of medication, or to flush the catheter. Unfortunately, the thumb-pump action is hard to control and the amount of flush dosage delivered is at the mercy of the coordination of the user's thumb. This only marginally solves the aforesaid problem in administering a calibrated dosage of saline IV flush, and consequently has not been widely adopted.
It would be greatly advantageous to provide a simple manually-operated mechanism capable of easy integration into otherwise-conventional roller-clamp regulators that will administer an accurate flush by allowing full flow of saline for a specific period of time (or volume) before returning to a “pre-flush” setting, eliminating the need to change the setting of the roller-clamp regulator or to administer a separate saline flush injection.